Manganous superoxide dismutase (MnSOD) plays an important role in oxygen metabolism of eukaryotic cells by scavenging toxic superoxide anion within the mitochondrion and catalyzing its conversion to peroxide. The mRNA encoding MnSOD can be induced in mammalian cells by the addition of the cytokine tumor necrosis factor (TNF). Because the gene encoding MnSOD is highly conserved from yeast to mammals, elements important for its transcriptional control in yeast may be homologous to elements in higher eukaryotes. This notion is bolstered by recent results showing that some yeast DNA-binding proteins recognize the same sequences as their mammalian homologs. Biochemical studies of the regulation of MnSOD protein from yeast have shown that its synthesis is positively regulated by oxygen, carbon source and heme, but little is known about the transcriptional regulation of the yeast gene encoding MNSOD (SOD1). In this proposal are outlined a series of molecular genetic and biochemical experiments using a SOD1-lacZ fusion to identify both the sequences necessary for positive and negative regulation of the SOD1 gene and the proteins which bind to these promoter sequences. Genetic methods for identifying other yeast genes important for the cell's response to oxidative stress are proposed.